Some search engines that search a document corpus (e.g., a group of web pages) collect information pertaining to which documents users find relevant for a particular search query (e.g., the documents viewed as results for a specific query). The collected information can be used to improve the rank of relevant documents in search results. However, when new documents are introduced into a corpus, very little information on their relevance for particular searches exists. Therefore, new documents which may be highly pertinent as results for a given query can have low search result rankings that make them less likely to be noticed by users.